Abstract

Physical inactivity is a major risk factor for complex metabolic diseases such as obesity, diabetes, and hypertension. Traditionally, these diseases and conditions have been the specific burden of adulthood, but they are now being diagnosed more frequently in younger populations. There has been some suggestion that, as is true in adults, children are becoming less physically active and that this decline in physical activity may help to explain the sudden increase in the incidence of metabolic diseases among children. Understanding the factors that are impacting on decreased physical activity levels in children will provide clues on how to approach this problem.Similar to findings in obesity, where obese parents tend to have overweight and obese children, physical activity appears to be related between parent and offspring. Although the literature regarding familial aggregation of physical activity levels is limited, it does allude to an association of physical activity levels among parents and children to varying degrees. Using several different approaches, we examined the familial resemblance of physical activity levels, determined by pedometry, in 96 extended Native American families from three geographic locations (Arizona, North/South Dakota, Oklahoma) in the Strong Heart Family Study. Based upon correlational analyses, physical activity levels were significantly and positively related among parent-offspring pairs. More specifically, correlations between father-daughter pairs (&lt,18 years of age) and father-son pairs (&gt,18-30 years of age) were rho = 0.30 and 0.26, respectively (p = 0.01). No significant associations were noted between physical activity levels of mother-offspring pairs. For our main investigation, we examined the familial effects, of physical activity using variance components analyses. Despite the fact that this study was conducted in three separate geographic locations, had limited household data, was not designed specifically to examine aggregation of physical activity levels, and was not limited to 2-parent families, when modeled as a heritable effect, physical activity achieved statistical significance (p = 0.007) explaining approximately 9% of the trait variance. Since physical activity can provide health benefits in youth, and since many young people are not meeting established guidelines, improving physical activity levels of youth is a key public health challenge. However, in order to develop effective physical activity interventions for youth, factors that impact on a child's physical activity levels need to be better understood. The findings of the current study indicate a significant, albeit weak, degree of aggregation of physical activity levels among parent-offspring pairs and among families. This supports the need to establish family based lifestyle interventions studies where both parent and child may benefit.